Trying to Make
3D into 2D: The illusion of Depth in 2D Artby David Rudd Cycleback

(c) cycleback 2003, 2005
all rights reserved

This 1400s Raphael painting uses many techniques
to give the sense of depth, including diagonal lines, diminishing
scale, placing objects top to bottom.

Creating the perception of depth in paintings, sketches and
photographs is a challenge, one that cannot be completely solved.
This is because depth is three dimensional, while a sketch, photographic
image or painting is two dimensional. Three dimensional depth
cannot physically exist in two dimensions. If you hold a crystal
clear family snapshot of the Grand Canyon in your hand, at least
logically you know that distant cliff and cloud is not miles
behind your hand. You know it is just an image on the surface
of a flat piece of paper.

Over the centuries artists have developed techniques to create
the representation of depth in 2D art. Before these techniques,
paintings and sketches lacked any sense of depth. Cave drawings
appear primitive as the artists didn't understand the standard
concepts of depicting depth. A European painting from 100 AD
shows objects in unreal proportions to each other. A mile away
person may be the same size as a person two feet away.

This page looks at a number of standard techniques used to
give paintings, sketches and other 2D art the illusion of depth.
These are techniques you can observe in art and incorporate into
your own art. These are also 'techniques' you can observe in
a real life, such as when looking at your living room or across
your back yard. After all, the art is attempting to duplicate
natural scenes like these.

Overlapping objects

An object appears to be in front of the object(s) it overlaps.
Overlapping is the strongest indicator of relative distance,
overriding all other signs when there is seeming conflict. In
the above Cezanne painting, the large center tree overlaps the
'distant' bridge, mountain and sky.

Diminishing scale
With things that are believed to be of same of similar size (2
cats or basketballs), the larger appears to be closer than the
smaller. In the left Cezanne painting, the viewer assumes that
the tree is much smaller than the distain hills. Thus the difference
in scale (tree taking up more space than the hills) makes it
appear as if the tree is closer. In the earlier Raphael painting,
the smaller people appear to be further away than the larger.
This is because the viewer is under the assumption people are
of similar.

Diagonal lines as diminishing scale
An exemplification of diminishing scale, diagonal lines moving
towards each other as they move up or down a painting or sketch
give the illusion of depth. A real world example of this is a
straight road that becomes skinnier as it approaches the distant
horizon. Another example is standing at one end of an empty hallway
and watching the lines where the wall and floor meet visually
move towards each other as they move to the other side of the
room.

This photo shows both diagonal lines and diminishing scale

Colors

Though not a set rule, in art humans tend to perceive bright,
warm colors like red, orange and yellow as being close, and dark,
cool colors like blue and dark purple as being further away.
The is particularly true for abstract art.

For landscapes, adding blue will make hills and mountains
look more distant. The further away the bluer. This is because
the color changes as it goes through more and more atmosphere.

In this photo, the hills become bluer, hazier and less focused
the further away.

Bottom to Top Placement of Ground and Top to Bottom Placement
of Ceilings

Barring conflicting inflicting information, humans generally
perceive what is at the bottom of painting to be in front, and
what is at the top to be in the back. This is particularly true
when looking outside where there is no 'ceiling.'

Top to bottom: the bottom outside fans appear to be closer
than fans and lights near the top. This is also an example of
diminishing scale, with the bottom fans being larger than the
top fans and, lights

Inside a building, the ceiling can have the opposite effect,
with the ceiling area nearest you appearing higher than the ceiling
area further away.

In this room, the floor appears to move up the further it
gets away from you. The ceiling (which is sort of like an upside
down floor) appears to move down. These are both the produce
of diminishing scale.

Focus

Things that are in focus tend to be perceived as closer than
things that are out of focus. This makes sense, as the books
on a road sign are too blurry to read if too far away. You must
drive closer to the sign to read it.

Similarly, objects that have more intense color, detail and
contrast often appear closer than objects that are blurrier,
hazier and having less focus.

In this old photograph depth is shown by diminishing scale,
the narrowing lines of the road and building tops, and that with
distance things become blurrier and hazier.

* * * *

Many visual illusions manipulate these techniques. The illusions
often use incongruous, logically conflicting techniques to toy
with our minds. One quality indicate one, while another will
evoke the opposite. One quality will evoke flatness, while another
will evoke great depth. The discord produces an emotional reactions
in the viewer. The illusion will appear 'impossible' or 'illogical'
to the viewer.

The natural signs of depth can also fool us in the real world.
Nature itself can give conflicting signs High in the mountains
beyond the haze we are used to, climbers often misjudge distance.
The mountain miles away is clear and unhazy and appears much
closer than it is. Climbers are often warned of this before the
climb, as the illusion can be dangerous Things like houses
appear larger and further away in heavy fog. It is the abnormal
haziness and blurriness that fools us In a movie, what
appears as a full sized house or ship or dinosaur often is a
miniature model. Carefully crafted sets make the things appear
many times larger than they are. A person will appear
shorter if photographed standing next to an extremely tall person
The moon appears larger when it is closer to the horizon
Gardens can be angled, planted groomed to make room appear
longer.

* * * *

A problem in trying to create realistic depth in two dimensions
is that the human is designed to detect real depth not a flat
representation. Looking at the real back yard, each eye looks
at the 3D objects from a different angle, the head and body movement
creating even more perspectives. The mind combines these different
views into the mind's image.

This cannot be done with a two dimensional object. With a
still life painting, and even a still life photograph, it is
not possible for the eyes to get the different views of the apple
that is needed to perceive a truly 3d orange. The photograph,
no matter how clear, shows only one perspective.

Notice that many attempts to create a closer to true 3D effect
involve an alteration not just to the flat image but to the viewer's
vision. 3D movies and pictures often require special glasses
and viewers.

The hologram is a rare example of a flat image that can realistically
simulate three dimensions, even allowing the viewer to see different
sides of a pictured object.

* * * *

Cubist art, where different sides of an object are seen in
painting, can be looked at as an attempt to represent 3Din a
2Dplane. Cubists sometimes also represented the passage of time,
with a figure being shown at different times.